U.S. patent application number 16/328757 was filed with the patent office on 2019-06-27 for method, apparatus and computer program for determining information on a position of an object, the object emitting a magnetic fi.
The applicant listed for this patent is FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V.. Invention is credited to Tobias DRAEGER, Jorn ESKILDSEN, Markus HARTMANN, Rafael PSIUK.
Application Number | 20190195658 16/328757 |
Document ID | / |
Family ID | 59799360 |
Filed Date | 2019-06-27 |
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United States Patent
Application |
20190195658 |
Kind Code |
A1 |
PSIUK; Rafael ; et
al. |
June 27, 2019 |
METHOD, APPARATUS AND COMPUTER PROGRAM FOR DETERMINING INFORMATION
ON A POSITION OF AN OBJECT, THE OBJECT EMITTING A MAGNETIC
FIELD
Abstract
A method for determining information on a position of an object,
the object emitting a magnetic field in response to an exciting
electromagnetic field comprises monitoring (100) a receive signal
of at least one loop antenna, the receive signal having a
contribution caused by the emitted magnetic field; determining a
first quadrature component (102) of the receive signal; and
determining the information on the position of the object (104)
based on the first quadrature component.
Inventors: |
PSIUK; Rafael; (Erlangen,
DE) ; HARTMANN; Markus; (Sulzbach-Rosenberg, DE)
; DRAEGER; Tobias; (Baiersdorf, DE) ; ESKILDSEN;
Jorn; (Torring, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG
E.V. |
Munich |
|
DE |
|
|
Family ID: |
59799360 |
Appl. No.: |
16/328757 |
Filed: |
August 31, 2017 |
PCT Filed: |
August 31, 2017 |
PCT NO: |
PCT/EP2017/071930 |
371 Date: |
February 27, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 63/004 20130101;
G01S 13/06 20130101; A63B 2024/0037 20130101; A63B 24/0021
20130101; A63B 2225/54 20130101; G01D 5/20 20130101; G01S 13/75
20130101; A63B 71/0605 20130101 |
International
Class: |
G01D 5/20 20060101
G01D005/20; A63B 71/06 20060101 A63B071/06; A63B 24/00 20060101
A63B024/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2016 |
DE |
10 2016 120 246.0 |
Claims
1. A method for determining information on a position of an object,
the object emitting a magnetic field in response to an exciting
electromagnetic field, comprising: monitoring a receive signal of
at least one loop antenna, the receive signal having a contribution
caused by the emitted magnetic field; determining a first
quadrature component of the receive signal; and determining the
information on the position of the object based on the first
quadrature component.
2. The method of claim 1, further comprising: subtracting a nulling
signal from the receive signal, the nulling signal being indicative
of a characteristic of the loop antenna without receiving the
emitted magnetic field.
3. The method of claim 1, further comprising: compensating a phase
and amplitude characteristic of the loop antenna within the receive
signal.
4. The method of claim 3, wherein compensating the amplitude and
phase characteristic comprises dividing the samples of the complex
valued receive signal by a complex valued calibration signal.
5. The method of claim 1, further comprising: determining the first
quadrature component of the receive signal at a first frequency;
determining a second quadrature component of the receive signal at
a second frequency; and determining the information on the position
of the object using the first quadrature component and the second
quadrature component.
6. The method of claim 5, further comprising: scaling the first
quadrature component or the second quadrature component by a
scaling factor.
7. The method of claim 6, wherein determining the information on
the position of the object comprises subtracting the second
quadrature component from the first quadrature component to
determine a corrected quadrature component.
8. The method of claim 7, further comprising: determining a change
of the corrected quadrature component; and compensating the change
of the corrected quadrature component if a characteristic of the
corrected quadrature component fulfills an error correction
criterion.
9. The method of claim 8, wherein compensating the change comprises
minimizing the corrected quadrature component.
10. The method of claim 8, wherein the error correction criterion
is fulfilled if the corrected quadrature component is below a
threshold.
11. The method of claim 8, wherein the error correction criterion
is fulfilled if a gradient of the change of the corrected
quadrature component is below a threshold.
12. The method of claim 8, wherein compensating the change
comprises: superimposing a correction signal on the receive
signal.
13. The method of claim 12, wherein the correction signal is phase
inverted with respect to the receive signal.
14. The method of claim 13, wherein an amplitude of the correction
signal deviates less than 5% from the amplitude of the receive
signal.
15. The method of claim 1, further comprising: exciting an
oscillating circuit of the object at a first frequency to emit the
magnetic field.
16. The method of claim 15, further comprising: exciting the
oscillating circuit of the object at a second frequency to emit the
magnetic field.
17. The method of claim 15, wherein the first frequency corresponds
to a resonance frequency of the oscillating circuit.
18. A computer readable storage medium, containing non-transitory
program code, that, when executed, determines information on a
position of an object, the object emitting a magnetic field in
response to an exciting electromagnetic field, in accordance to the
method of claim 1.
19. A signal evaluation processor for determining information on a
position of an object, comprising: a signal input configured to
monitor a receive signal, the receive signal being received by at
least one loop antenna and having a contribution caused by an
emitted magnetic field, the emitted magnetic field being emitted by
the object in response to an exciting electromagnetic field; a
signal processing circuit configured to determine a first
quadrature component of the receive signal; and a signal evaluation
circuit configured to determine the information on the position of
the object based on the first quadrature component.
20. The signal evaluation processor of claim 19, wherein the signal
processing circuit is configured to determine the first quadrature
component of the receive signal at a first frequency; and to
determine a second quadrature component of the receive signal at a
second frequency; and wherein the signal evaluation circuit is
configured to determine the information on the position of the
object using the first quadrature component and the second
quadrature component.
Description
BACKGROUND
[0001] Embodiments relate to a method for determining information
on a position of an object which emits a magnetic field.
[0002] Applications, where objects are monitored with respect to
their movement and position are numerous, as for example in sports
games. Sports games, such as for example soccer, football,
handball, ice hockey, hockey or the like employ rules where one
participating party scores when an object, such as a ball or the
like, crosses a predetermined detection plane, as for example the
open front face of a goal in soccer. The information, whether the
ball completely passed the plane bordering the goal is essential to
conclude whether the score has been achieved or not. Traditionally,
that decision has been taken by a referee from a visual
observation. Especially in scenarios where the ball moves into the
direction of the goal and is returned quickly by the goal keeper,
it may be difficult to determine, whether the ball entered
completely into the goal, which is whether the ball moved
completely through the detection plane. For example, in sports
games, it may, therefore, be of interest to determine information
on the position of a ball, a puck or other sports equipment, be it
relative with respect to another item or participant of the sports
game or be it in absolute coordinates.
[0003] There exist some approaches to determine the object's
position. Apart from camera-based optical systems, some approaches
propose to detect the transition of the ball through a detection
plane, e.g. the plane defined by the goal line, using
electromagnetic fields and/or signals derived therefrom. Some
proposed systems provide magnetic fields of different direction on
opposite sides of the detection plane together with sensors within
the object or the ball under observation. That is, a sensor within
the object monitors the magnetic field and actively determines that
it passed through the detection plane when the orientation of the
magnetic field has changed. In that event, the object or a sender
contained therein transmits the information that the object
detected transition through the detection plane to a receiver
circuit such as to be able to indicate whether the ball was fully
inside the volume of the goal or not.
[0004] Other systems utilize two antenna loops on each side of the
detection plane, wherein each antenna loop receives a
high-frequency signal with opposite phase such as to provide
magnetic fields cancelling each other out in the detection plane in
the middle between the two loops. A third receive antenna loop is
deployed at this position in order to receive the field disturbance
of an object passing through the set-up such as to be able to
conclude, on occurrence of a signal on the receive antenna loop,
that a ball or an object passed the plane of the receive antenna
loop.
[0005] In order to provide or to receive the magnetic field used
for the detection, those systems utilize antenna loops fully
encircling the area of interest within the detection plane, such as
for example the open mouth of a soccer goal in order to provide a
field of precisely predetermined geometry. By relying on the
precise generation of a magnetic field of predetermined geometry,
in particular with respect to the detection plane where a
disappearing magnetic field is required, those systems suffer from
a decreased spatial resolution, since the generation of such a
precise field configuration over large areas is hardly feasible.
Further, those conventional systems are sensitive to disturbances
of the electromagnetic field which may, for example, be caused by
items of conductive material, which can be excited to generate a
magnetic field. Generally, disturbing objects that have the
capability to also emit a magnetic field may disturb or prevent the
generation of the information on the position of the object of
interest.
[0006] That is, there is a desire to provide a method for
determining information on a position of an object being more
robust.
SUMMARY
[0007] An embodiment of a method for determining information on a
position of an object, the object emitting a magnetic field in
response to an exciting electromagnetic field, comprises monitoring
a receive signal of at least one loop antenna, the receive signal
having a contribution caused by the emitted magnetic field. The
method further comprises determining a first quadrature component
of the receive signal. The information on the position of the
object is determined based on the first quadrature component. In
using the quadrature component of the receive signal, signal
contributions of disturbing objects can be suppressed or even
eliminated, which predominantly contribute to the in-phase
component of the receive signal.
[0008] Some embodiments comprise determining the first quadrature
component of the receive signal at a first frequency and
determining a second quadrature component of the receive signal at
a second frequency, while the information on the position of the
object is determined using the first quadrature component and the
second quadrature component. By using two different frequencies,
signal contributions of disturbing objects may be suppressed to a
greater extent in applications where the signal contribution of the
object is big at one of the first or the second frequencies while
it is small at the other frequency so that equal signal
contributions of disturbing objects at both frequencies can be
compensated.
[0009] Some embodiments comprise determining a change of the
corrected quadrature component as wells as compensating the change
of the corrected quadrature component if a characteristic of the
corrected quadrature component fulfills an error correction
criterion. If a change of the quadrature component is compensated
while an error correction criterion indicates that the change is
not caused by a signal emitted by the object, long term deviations
from stable operating conditions, caused for example by temperature
or other environmental changes, may be considered and corrected
for. This may enable stable operating conditions resulting with
good positioning results over extended periods of time, also at
varying operating conditions.
BRIEF DESCRIPTION OF THE FIGURES
[0010] Some embodiments of apparatuses and/or methods will be
described in the following by way of example only, and with
reference to the accompanying figures, in which
[0011] FIG. 1 shows a schematic view of a goal of a soccer field
having mounted thereto an antenna system for monitoring signals
caused by an object emitting a magnetic field;
[0012] FIG. 2 shows a sideview of a section of the antenna system
as attached to the goal;
[0013] FIG. 3 shows an example of idealized signal characteristics
of an excitation signal used to make the object emit a magnetic
field and the receive signal caused by the emitted magnetic
field;
[0014] FIG. 4 shows a perspective view of an example of an antenna
system usable to monitor receive signals;
[0015] FIG. 5 shows a circuit diagram of an example of an antenna
system;
[0016] FIG. 6 shows an implementation of a calibration signal
generator for generating a calibration signal;
[0017] FIG. 7 shows an embodiment of a sports equipment operable to
emit an electromagnetic field according to the present
invention;
[0018] FIG. 8 shows a flow chart of an embodiment of a method for
determining information on a position of an object;
[0019] FIG. 9 illustrates a signal characteristic of a receive
signal used to determine the information on the position of the
object; and
[0020] FIG. 10 illustrates a flowchart of further optional steps of
the method for determining information on a position of the
object.
DETAILED DESCRIPTION
[0021] Various examples will now be described more fully with
reference to the accompanying drawings in which some examples are
illustrated. In the figures, the thicknesses of lines, layers
and/or regions may be exaggerated for clarity.
[0022] Accordingly, while further examples are capable of various
modifications and alternative forms, some particular examples
thereof are shown in the figures and will subsequently be described
in detail. However, this detailed description does not limit
further examples to the particular forms described. Further
examples may cover all modifications, equivalents, and alternatives
falling within the scope of the disclosure. Like numbers refer to
like or similar elements throughout the description of the figures,
which may be implemented identically or in modified form when
compared to one another while providing for the same or a similar
functionality.
[0023] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, the elements may
be directly connected or coupled or via one or more intervening
elements. If two elements A and B are combined using an "or", this
is to be understood to disclose all possible combinations, i.e.
only A, only B as well as A and B. An alternative wording for the
same combinations is "at least one of A and B". The same applies
for combinations of more than 2 Elements.
[0024] The terminology used herein for the purpose of describing
particular examples is not intended to be limiting for further
examples. Whenever a singular form such as "a," "an" and "the" is
used and using only a single element is neither explicitly or
implicitly defined as being mandatory, further examples may also
use plural elements to implement the same functionality. Likewise,
when a functionality is subsequently described as being implemented
using multiple elements, further examples may implement the same
functionality using a single element or processing entity. It will
be further understood that the terms "comprises," "comprising,"
"includes" and/or "including," when used, specify the presence of
the stated features, integers, steps, operations, processes, acts,
elements and/or components, but do not preclude the presence or
addition of one or more other features, integers, steps,
operations, processes, acts, elements, components and/or any group
thereof
[0025] Unless otherwise defined, all terms (including technical and
scientific terms) are used herein in their ordinary meaning of the
art to which the examples belong.
[0026] FIGS. 1 to 4 illustrate an example of an antenna system that
may be used to determine information on a position of a ball with
respect to a soccer goal to illustrate the principles allowing to
determine information on a position of an object that emits a
magnetic field. However, this application is to be understood as
one particular example only since various other applications may
use an embodiment of a method for determining information on a
position of an object.
[0027] FIG. 1 shows a schematic view of a goal, e.g. of a soccer
game, having mounted thereto four antenna systems 2a-d. Although
the goal is enclosed by four antenna systems in FIG. 1, further
examples may also utilize different amounts of antenna systems. For
example, in a further example, only one antenna system may be used,
either at one of the posts of the goal or at the top bar of the
goal. In the example of FIG. 1, the antenna system serves to
determine the transit of a ball through the detection plane defined
by the goal line. In the configuration of FIG. 1, the detection
plane is the plane perpendicular to loop antennas 4a-d of the
antenna systems 2a-d and, therefore, parallel to the open front
face of the goal.
[0028] As elaborated on in the following description of FIGS. 2 to
6, the loop antennas 4a-d are the antennas used for the detection
of the crossing or of the transit of the ball 11 through the
detection plane. Therefore, the loop antennas 4a-d may also be
denoted as goal line antennas. While the following simple examples
will mainly address the crossing of the detection plane, the
embodiments using the receive signals of the loop antennas may also
derive more elaborate information on the position of the ball. For
example, some embodiments may determine the coordinate of the ball
using, for example, a fingerprinting technique where an expected
quadrature component of the receive signal for various positions of
the ball is--for each of the loop antennas--compared to the
received quadrature component to conclude on the position of the
ball.
[0029] The example of FIG. 1 further comprises a further loop
antenna 6a-d in each of the antenna systems 2a-d, which comprises
one or more antenna loops arranged only within a further antenna
plane which is perpendicular to the antenna plane of the loop
antennas 4a to 4d and parallel to the detection plane 22. These
further loop antennas may serve to derive information whether the
ball passed through the detection plane 22 inside the goal or
outside of the goal. Therefore, the further loop antennas 6a-d may
also be denoted as frame antennas. In other words, the frame
antennas serve to define an area of interest within the detection
plane, in order to be able to conclude, whether the ball crossed
the detection plane within the area of interest. Therefore, the
further loop antennas 6a-d are situated at the border of the area
of interest, that is, at the goal posts. Alternatively, the area of
interest may be determined using the loop antennas 4a-4d together
with a finger-printing technique.
[0030] FIG. 1 further illustrates schematically a ground loop
signal path 8, which serves to connect first and second terminals
of the loop antennas 4a-d such as to close a conductive loop in
order to generate an exciting electromagnetic field as illustrated
in FIG. 2. That is, the ground loop signal path 8 closes the
electrical circuit in order to enable the generation of the
exciting electromagnetic field with the loop antennas 2a-d.
[0031] Although the example illustrated in FIG. 1 utilizes the loop
antennas 4a-d to also generate the exciting electromagnetic field
by applying an excitation signal to said loop antennas 4a-4d,
further examples may utilize a separate excitation loop in order to
provide the exciting electromagnetic field. According to some
examples, the separate excitation loop extends through the center
of the loop antennas 4a-4d.
[0032] In the following, the operating principles of the antenna
system and of the determination of the presence of a crossing or of
a transit of an object through the area of interest within the
detection plane 22 will be explained together with the discussion
of FIGS. 2 to 6.
[0033] With the antenna system, an exciting electromagnetic field
is generated that has filed lines of the magnetic component that
cross the detection plane 22 essentially perpendicular to the
detection plane 22. The exciting electromagnetic field 10 or, to be
more precise, its magnetic component is only illustrated
schematically by indicating the direction of a single field line 10
in FIG. 2.
[0034] Utilizing an object 11 emitting a magnetic field 12 as
illustrated in FIG. 2, the magnetic component 12 of the
electromagnetic field is received by means of the loop antennas
4a-d. FIG. 2 assumes the object 11 to be a ball of sports game
which emits the magnetic field 12 as illustrated by the shown field
lines. This may in principle be achieved by using an object 11 or a
ball which is actively sending a magnetic field 12.
[0035] The examples described in the Figs, however, utilize a ball
11 or an object which is excited by the exciting electromagnetic
field 10 as generated by the loop antennas 4a-d to emit the
magnetic field 12. To this end, a ball or object 11 as shown in
FIG. 10, left illustration, may be utilized, which comprises three
loop antennas 14a-c being arranged in a pairwise perpendicular
orientation with respect to each other. The three loop antennas
14a-c are connected in series with each other and with a resonator
or oscillation circuit 16, the resonator 16 having a resonance
frequency corresponding essentially to a first frequency of the
exciting electromagnetic field 10. That is, the object comprises
three perpendicular coils 14a-c with a resonance frequency
corresponding to the first frequency of the exciting
electromagnetic field 10. When such a ball or object 11 approaches
the goal or the antenna system 2a-d, the coils 14a-c inside the
ball 11 are stimulated by the exciting electromagnetic field 10.
That is, a current is induced in the loop antennas 14a-c. Due to
the resonance frequency of the resonator of the object 11 and the
corresponding frequency of the exciting electromagnetic signal 10,
the received energy is stored in the resonant circuit or in the
resonator 16 of the object, e.g. in a capacitor used therein. The
oscillation in the resonator or the stored energy is then
generating a magnetic field in the coils 14a-c of the object 11
itself, having field lines 12 with a direction opposite to the
direction of the field lines of the exciting electromagnetic field
10.
[0036] According to further examples, the object may also comprise
three loop antennas or coils 14a-c which are being arranged in a
pairwise perpendicular orientation with respect to each other and
which are not connected in series, as indicated by the right
illustration in FIG. 10. Each loop antenna or coil 14a-c is part of
an independent resonator which further comprises an associated
capacitance 16a-c being connected in series or in parallel. Each of
the three so provided resonant circuits may be tuned to the
frequency of the exciting electromagnetic field 10 by choosing the
capacitances and the inductances of the loops of each circuit
appropriately. Other embodiments, however, may use different
resonance frequencies for each of the independent resonators to be
able to distinguish the individual coils and to so determine
information on an orientation of the ball.
[0037] Due to the properties of the resonator, the magnetic field
12 emitted by the object 11 is delayed with respect to the exciting
electromagnetic 10 field by a time corresponding to a phase shift
of 90.degree. (.pi./2) if the resonator is tuned to the frequency
of the exciting electromagnetic field 10. This stimulation of the
emission of a magnetic field 12 is also utilized in Radio Frequency
Identification systems (RFID) in order to transmit information from
objects not having embodied own energy sources. In RFID, the
excited emission of a magnetic field 12 as illustrated in FIG. 2 is
also known as "backscattering". The backscattered or emitted
magnetic field 12 of the object 11 is, amongst others, received by
the loop antenna 4c which is mounted behind a goal post or a bar 18
of a goal. While the loop antennas 4a-d of the antenna systems
illustrated in the Figs. do only comprise one single antenna loop
formed by a conductor, further examples may also utilize loop
antennas having more loops. FIG. 3 illustrates an idealized phase
relation between an excitation signal 28 used to generate the
exciting electromagnetic field 10 and a receive signal 29 as it may
be received at a signal terminal of the loop antenna 4c.
[0038] Utilizing an object 11 as, for example the one illustrated
in FIG. 10 leads to a field configuration of the magnetic field 12
emitted by the object 11 as illustrated in FIG. 2. This is due to
the cause that the individual electromagnetic fields emitted by the
three loop antennas 14a-c superimpose with each other such as to
arrive at the field configuration of FIG. 2. One exemplary field
strength vector 20 of the emitted magnetic field 12 is illustrated
in FIG. 2, which is composed of a first component 20a in parallel
to the detection plane 22 as well as of a second component 20b
perpendicular to the detection plane 22. Due to its orientation,
the loop antenna 4c is sensitive to the first component 20a, which
is, therefore, also denoted as the goal line part, whereas the
second component 20b is also denoted as the frame part of the field
strength vector 20 (H.sub.back,ball).
[0039] In other words, the backscatter signal of the object 11 or
the ball is inducing a current into the loop antenna 4c and the
further loop antenna 6c of the antenna system 2c. The signal within
the loop antenna 4c (caused by the first component of the field
strength vector 20) is subsequently evaluated as the receive signal
to determine the information on the position of the object. The
further loop antenna 6c, therefore, is only illustrated
schematically and for the sake of completeness in FIG. 2. The
backscattered or received signal can be split into a frame part 20b
and a goal line part 20a. Depending on the position of the ball,
the orientation of the H-field vector 20 of the backscatter signal
is changing. As soon as the ball is passing the detection plane 22
at the center of the loop antenna 4c, the first component 20a of
the field strength vector (H.sub.back,goal) is crossing zero and
the signal waveform is inverted. That is, a phase condition of the
receive signal changes according to a predetermined condition. The
predetermined condition is, according to the example of FIGS. 2 to
6, that the signal waveform is inverted and that the phase
undergoes a change of 180.degree.. Once a phase inversion or a
phase shift of 180.degree. occurs or is determined by evaluation of
the receive signal provided by the antenna system 2c, in particular
by the loop antenna 4c, a goal could in principle be assumed, since
the center of the ball or of the object 11 crossed the line of
symmetry of the two signal paths of the loop antenna 4c, that is
the detection plane 22. At the time of the crossing, the overall
field strength of the exciting electromagnetic field 12 is at
maximum and, therefore, the emission of the magnetic field 12 of
the object is maintained, increasing the achievable precision in
the determination of the transit of the object 11 as compared to
alternative approaches, where the exciting electromagnetic field
within the detection plane 10 is tuned or adjusted to be zero.
[0040] However, at the presence of unavoidable disturbing objects,
the accuracy of the determination of the crossing of the object may
not be high enough, since the disturbing objects themselves may
cause a magnetic field in parallel to the first component 20a of
the field strength vector, so potentially falsifying the simple
determination of the crossing of the ball according to the
previously described approach.
[0041] According to the embodiments to determine information on the
position of the object subsequently described in connection with
FIGS. 8 to 10, the information on the position of the object may be
determined even at the presence of disturbing objects. The
determination may be based on the receive signals received or
monitored by means of the loop antennas of the example
configurations illustrated in FIGS. 1 to 6.
[0042] For the detection of a goal in a soccer game, the antenna
system 4c may comprise a mounting structure operable to mount the
antenna system to a support structure or to the goal such that the
detection plane 22 has a distance equaling half a diameter of a
soccer ball to the front face of the goal. In order to provide a
more flexible solution, the mounting structure may be adjustable to
fit different designs of goals, such as to be able to adjust the
predetermined distance to the requirements. FIG. 4 shows a
perspective view of the configuration illustrated in FIG. 2,
wherein an example of a mounting structure 24 adapted to mount the
antenna system comprising the loop antenna 4c and the further loop
antenna 6c to the aluminum bar 18 of a goal is illustrated
schematically.
[0043] As further illustrated in FIG. 4, the loop antenna 4c
comprises a first terminal 26a and a second terminal 26b in order
to receive the excitation signal 28 for the loop antenna 4c, which
allows providing said excitation signal 28 to the loop antenna. As
illustrated in more detail in FIG. 4, the excitation signal 28 of
alternating current is split and transferred (propagates) from the
first terminal 26a to the second terminal 26b via a first signal
path 30a as well as via a second signal path 30b. That is, both
conductors of the loop antenna 4c which extend in parallel to the
detection plane 22 participate in the generation of the exciting
electromagnetic field 10. According to the example of FIG. 4, the
further loop antenna 6c, that is, the frame antenna, does not
participate in the generation of the electromagnetic field 10.
However, further examples may also utilize the further loop antenna
6c for the generation of the exciting electromagnetic field 10.
[0044] FIG. 4 further illustrates a compensation signal path 32,
which is coupled to the second signal path 30b and which serves to
balance the loop antenna 4c. In alternative examples, the
compensation signal path 32 may, of course, also be coupled to the
first signal path 30a. The compensation signal path 32 has
adjustable coupling characteristics with respect to the second
signal path 30b. This may be utilized to compensate for field
components generated by eddy currents in metallic posts such as for
example in the aluminum post 18 illustrated in FIG. 4. The eddy
currents may, for example, be generated by the current in the first
signal path 30a and, hence, induce a current into the loop antenna
4c which is not caused by the object and, therefore, undesirable.
By means of the compensation signal path 32, or, more generally, by
using a compensation signal generator within the antenna system 2c,
such signal components may be compensated so that the antenna is
balanced, that is, one of the signal paths 30a or 30b carries half
of the current of the excitation signal 28, while the other signal
path, possibly together with the compensation signal path 32 or
with the compensation signal generator carries the other half of
the current, such that no signal as induced in the loop antenna 4c
without the presence of the object 11 in the proximity of the loop
antenna 4c. To this end, the loop antenna is tuned such that the
both signals carrying half of the current each are in phase.
[0045] FIG. 4 shows one particular possibility to implement a
compensation signal generator by using a compensation wire having
an adjustable distance to the wire of the second signal path 30b
and/or an adjustable inductance so that the antenna can be balanced
by adjusting the distance and/or the inductance once the antenna is
mounted to the support structure or to the goal. A further
possibility to implement a compensation signal generator would, for
example, be to add a symmetric metal or aluminum part on the other
side of the antenna system 2c such as to provide a symmetric
configuration in which the eddy currents of the different metal
bars compensate each other. A further possibility to implement a
compensation signal generator would, for example, be to induce a
current into the loop antenna 4c or into one signal path of the
loop antenna 4c with an appropriately adjusted amplitude and phase
generated such that the influence of the eddy current is
compensated for. The induction of this additional compensation
signal could, for example, be performed by means of a further
transformer or the like. However, when using a compensation signal
path 32 or a compensation wire as illustrated in FIG. 4, and, in
more detail in FIG. 5, no further active signal path is necessary
and, hence, the antenna system remains simple and reliable.
[0046] Apart from the use of the compensation signal generator or
the compensation signal path 32, the antenna system design is also
highly efficient in avoiding cross-talk or undesired signal
components as compared to other solutions employing an additional
independent loop for the generation of the exciting electromagnetic
field 10. Using an additional loop may generate cross-talk signals
in the loop antenna 4c of the antenna system 2c which might cover
the magnetic field 12 of the backscatter signal of the object 11.
This would decrease the accuracy of the detection of the occurrence
of a goal significantly. However, utilizing the loop antenna to
create the exciting electromagnetic field as in the examples
described in the Figs. avoids the occurrence of cross-talk signals
due to the particular generation of the exciting electromagnetic
field 10.
[0047] FIG. 5 shows a circuit diagram of an example of an antenna
system. For the simplicity of the illustration, only the loop
antenna 4c is illustrated in FIG. 5, while the further loop antenna
6c, that is the frame antenna, is not shown, since this antenna
need not be balanced or compensated with the same precision as the
goal line antenna 4c. The loop antenna comprises the first signal
path 30a and the second signal path 30b. The transmission
properties of the first and second signal paths 30a and 30b are
illustrated by corresponding first and second inductances 46a and
46b as well as by corresponding first and second resistances 48a
and 48b. As already mentioned before, the excitation signal 28 is
split at the first terminal 26a such as to utilize both signal
paths 30a and 30b for the generation of the exciting
electromagnetic field 10. The signal of both signal paths 30a and
30b is summed up at the second terminal 26b where the current
source providing the excitation signal 28 connects. The influence
of metallic post of a goal or the like is modelled by the inductive
coupling between an inductance 50 of the aluminum post which is
connected in series to an associated resistance 52. In order to
compensate for the influence of the post the antenna system
illustrated in FIG. 5 incorporates a compensation signal path 32,
connected in parallel to the second signal path 30b. The
compensation signal path 32 has associated thereto an inherent
resistance 54 and an inherent inductance 56. A distance between the
compensation signal path 32 and the second signal path 30b may,
according to some examples, be adjustable in order to compensate
for the influence of the eddy currents in the aluminum post.
According to further examples, the compensation signal path 32 may
furthermore comprise a variable inductance 58, such as to be able
to compensate the influence of the aluminum post or of other
influences more precisely. In other words, an additional wire may
be used, which is running or extending in parallel to the second
signal path 30b of the antenna loop 4c and which builds a coupling
circuit (L.sub.goal2, L.sub.comp, M.sub.com,var). By changing the
distance between the compensation wire and the antenna loop 4c, the
coupling factor M.sub.comp,var can be adjusted. In addition or
alternatively, a variable inductor 58 or a variable capacitance may
be implemented into the compensation path 32. The two variable
elements L.sub.comp,var and M.sub.comp,var may be tuned in a way
that both sides of the loop, that is, the first signal path 30a at
the first side of the detection plane 22 and the second signal path
30b in combination with the compensation signal path 32 at the
opposite side of the detection plane 22 are balanced. That is, in
the balanced situation, I.sub.TX1=I.sub.TX2=1/2*I.sub.exc, with the
current signals being in phase.
[0048] The loop antenna 4c furthermore comprises a signal terminal
60 comprising a first signal terminal 60a and a second signal
terminal 60b in order to provide the receive signal of the loop
antenna 4c. The receive signal is coupled out of the loop antenna
4c by means of a transformer 62. The transformer 62 is formed by a
first coil 64a and a second coil 64b as well as by a third coil 66.
The first coil 64a is part of the first signal path 30a and the
second coil 64b is part of the second signal path 30b, wherein the
first terminal 28 is situated between the first and second coils
64a and 64b. The first and second coils 64a and 64b are, however,
wound with different orientations, that is, the third coil 66 is
coupled to the first and second coils 64a and 64b such that
essentially no current is induced in the third coil 66 when the
current through the first and second coils 64a and 64b is
essentially equal, that is, when the antenna is balanced.
Therefore, in the situation of a balanced antenna, no current is
induced in the third coil 66 and hence no significant receive
signal is provided at the first and second signal terminals 60a and
60b when the object is not present or close.
[0049] In order to be able to perform the above discrimination of
the receive signal 29 and hence the determination of a transit of
the ball 11 through the detection plane 22, however, knowledge on a
phase relation between the excitation signal 28 and a receive
signal 29 as provided at the signal terminals 60a and 60b may be
desirable. Arbitrary amplitude and phase distortion may be employed
due to a delay in the antenna cables or in the receiving path of a
receiver coupled to the signal terminal 60. These may need to be
compensated. In the desirable configuration of a fully-balanced
antenna system, however, no signal is present at the signal
terminals 60a and 60b which may be utilized for the determination
of the phase relation.
[0050] In order to provide for the possibility of such a
calibration, further examples of the present invention optionally
comprise a calibration signal generator 69 which is operable to
modify the characteristics of the antenna system such that a signal
is generated at the signal terminals 60a and 60b.
[0051] According to some examples, this may be achieved by
switchable tuning elements in one of the first or the second signal
paths 30a or 30b to intentionally bring the antenna out of balance.
Examples of those tuning elements may be additional inductors or
coupling elements which can be switched on and off by means of
relays or transistor circuits. That is, according to some examples,
the calibration signal generator 69 may comprise a calibration
circuit being coupleable to the first or the second signal path 30a
or 30b on demand.
[0052] According to another example, the calibration signal
generator 69 allows to change the configuration of the circuitry
used to generate the exciting electromagnetic field 10 such that
the changed exciting electromagnetic field 10 induces a minor
amount of current into the loop antenna 4c and, optionally, also in
the further loop antenna 6c (the frame antenna). Different exciter
loop configurations may be changed by means of a relay or
transistor circuitry, which is capable of switching between at
least two different configurations. According to the example of
FIG. 6, the calibration signal generator 69 is operable to select
one of two different ground loop signal paths 70a and 70b. In the
configuration of the first ground loop signal path 70a, the field
vector 72 of the magnetic component of the exciting electromagnetic
field 10 as created by the loop antenna 4c is, at the detection
plane 22, perpendicular to said detection plane 22 and, therefore,
no signal is induced into a balanced loop antenna 4c. In the second
configuration, as illustrated in the lower illustration of FIG. 6,
however, a second ground loop signal path 70b is chosen such that
the field vector 72 is slightly inclined and, hence, a signal is
induced in the loop antenna 4c. The so induced signal may be
utilized to determine the phase relation between the exciting
signal 28 and the receive signal 29.
[0053] The antenna system of FIG. 5 further comprises a signal
evaluation processor 68 coupled to signal terminal 60 of the
antenna system to monitor the receive signal and to determine
information on the position of the object and/or on the transit of
the object through the detection plane 22.
[0054] FIG. 7 shows an example of sports equipment or a sensor
configuration to be used with an antenna system as previously
described and which emits a magnetic field 12 used to determine the
transit of the sports equipment through the detection plane 22 or
to localize the object illustrated in FIG. 7 in space. The object
or sports equipment of FIG. 7 comprises three pairwise
perpendicular antenna loops 14a to 14c which are connected in
series with a resonator or oscillating circuit 16 having a
resonance frequency corresponding essentially to the frequency of
an exciting electromagnetic field 10. According to some
embodiments, the resonance frequency is within the range of 10 kHz
to 300 kHz or, preferably, in the range of 30 kHz to 200 kHz, such
as to use electromagnetic fields not being disturbed by the
presence of human beings, animals or other living creatures so that
a reliable detection of a goal or the object may be performed, even
when the area of the goal is crowded with soccer players or other
people. While FIG. 7 illustrates a ball for a soccer game as an
object to be localized, further embodiments may also use other
sports equipment comprising antenna loops and an associated
oscillating circuit 16. For example, hockey balls, ice hockey pucks
or handballs may be objects to be localized in further embodiments.
In some examples, such as for example objects being not point
symmetric, the coils may not necessarily be of the same size and/or
the oscillating circuits of the different coils may be tuned to
different frequencies to allow to distinguish the magnetic field
emitted by the different coils from one another.
[0055] With respect to FIGS. 8 to 10 it will subsequently be
explained how some embodiments determine information on a position
of an object based on a receive signal, which may, for example, be
generated as elaborated on in the preceding paragraphs.
[0056] FIG. 8 illustrates a flow chart of an embodiment of a method
for determining information on a position of an object. The method
may, for example, be performed by signal evaluation processor
68.
[0057] In order to determine the information on the position of the
object, the receive signal is monitored 100 and a first quadrature
component of the receive signal is determined in step 102. The
information on the position of the object is determined in step 104
based on the first quadrature component. In using the quadrature
component (Q-component) of the receive signal as opposed to both,
the quadrature and the in-phase component (I-component), signal
contributions of disturbing objects can be suppressed or even
eliminated, as illustrated by means FIG. 9.
[0058] FIG. 9 illustrates the current generated within the object
illustrated in FIG. 7 as a function of the frequency of the
exciting magnetic field. The oscillation circuit within the object
is tuned to a resonance frequency corresponding to the first
frequency of 119 kHz. The first graph of FIG. 9 illustrates the
in-phase component 120 of the current while the second graph
illustrates the quadrature component 140 of the current. The
Q-component 140 is maximum when the oscillation circuit is excited
at its resonance frequency while the I-component is zero. When
exciting an oscillating circuit of the object at a first frequency
equal to the resonance frequency of the object, the object emits a
magnetic field with a phase shift of 90 degree with respect to the
exciting electromagnetic field. In this context it is worth noting
that the in-phase and quadrature components are to be understood
with respect to phase condition of the exciting magnetic field,
which is to the phase of a current in a coil generating said field.
In other words, the I-component 120 of the current of FIG. 9 has an
identical phase as the exciting electromagnetic field or the
current generating said field.
[0059] The emitted magnetic field if the object directly couples
into the receive antenna so that no further phase shifts apply. The
contribution of the emitted magnetic field of the object to the
receive signal is, therefore, maximum in the Q-component of the
receive signal. Ideally the contribution of the I-component would
be zero. However, minor imperfections of the system may also lead
to smaller contribution of the I-component. One possibility to
determine the I-component and the Q-component of the receive signal
is to downmix the receive signal using the signal that is used to
generate the exciting magnetic field as an Local Oscillator (LO)
Signal. Both, the I-Component and the Q-component are then
constituting a complex valued receive signal. The complex valued
representation of the receive signal is another representation of
the receive signal and the processing of the receive signal may be
based on both, the directly received signal or on its complex
valued representation.
[0060] FIG. 9 further illustrates that the Q-component of a current
generated in an object rapidly decreases when the frequency of the
exiting magnetic field veers away from the resonance frequency of
the object. For example, at an excitation with the second frequency
132 of 134 kHz, the Q-component 140 of the current is almost
negligibly small when compared to the Q-component of an excitation
at resonance frequency. Disturbing objects that may also be excited
by the exciting magnetic field (for example developing eddy
current) do only contribute to a small amount of the Q-component of
the receive signal and mostly contribute to the I-component. Using
the Q-component of the receive signal to determine the information
on the position of the object may hence result with highly accurate
localizations since the contributions of unwanted yet unavoidable
disturbing objects are suppressed. Even dynamically occurring
disturbing objects are considered, since the monitored receive
signal predominantly has a contribution from the object within the
quadrature component (Q-component) of the receive signal.
[0061] According to some embodiments, some characteristics of the
receiving loop antenna are compensated to further increase the
accuracy of the measurement.
[0062] According to some embodiments, a nulling signal is
subtracted from the receive signal. The nulling signal is
indicative of a characteristic of the loop antenna without
receiving the emitted magnetic field of the object. The nulling
signal can be measured while the exciting magnetic field is
generated but without the presence of an object to be located. The
receive signal may then comprise contributions from direct coupling
between an exciting antenna loop used to generate the exciting
magnetic field and the receiving loop antenna or from static
interferers or disturbing objects. In subtracting the nulling
signal, these contributions may be suppressed.
[0063] According to further embodiments, the method comprises
compensating a phase and amplitude characteristic of the loop
antenna within the receive signal. Considering the individual phase
and amplitude characteristic of a loop antenna and eventually its
associated signal processing chain may further increase the
positioning accuracy.
[0064] The amplitude and phase characteristic may be determined by
a calibration object or by an actively emitting calibration loop
emitting a magnetic calibration field with constant phase relation
to the exciting electromagnetic field. Measuring the calibration
field with the loop antenna and determining it's measured amplitude
and phase allows to compensate undesired damping and phase
alterations of the antenna loop presently calibrated. According to
some embodiments, compensating the amplitude and phase
characteristic comprises dividing the samples of a complex valued
receive signal by a complex valued calibration signal. The complex
valued calibration signal may be determined by dividing the
measured complex valued signal by the expected complex valued
signal at the presence of the calibrating magnetic field.
[0065] Calibrations of the antenna may, for example, be important
when the information of multiple loop antennas is combined to
conclude on a position of the object, for example in an approach
relying on fingerprinting.
[0066] FIG. 10 illustrates a flowchart of a further embodiment of a
method for determining information on a position of an object that
is excited using two frequencies to generate the exciting
electromagnetic field. This may be achieved by operating the
exciter loop with two frequencies, either simultaneously or
alternatingly. That is, the oscillating circuit of the object is
excited at a first frequency to emit the magnetic field and the
oscillating circuit of the object is excited at a second frequency
to emit the magnetic field. The first frequency 130 corresponds to
the resonance frequency of the oscillating circuit of the object
and the second frequency 132 has an appropriate distance, for
example being more than 5% or more than 10% of the first frequency
apart from the first frequency. Another way to determine an
appropriate distance is to assure that the Q-component within the
receive signal received while exciting the object at the second
frequency is smaller than a predetermined fraction of the Q
component received while exciting the object at the first
frequency. According to some embodiments, the predetermined
fraction is chosen to be 70%, 50%, 30%, 10% or less.
[0067] The method according to the embodiment illustrated in FIG.
10 comprises determining the first quadrature component 160 of the
receive signal at a first frequency and determining a second
quadrature component of the receive signal at a second frequency
162. The determination of the information on the position of the
object uses both, the first quadrature component and the second
quadrature component. Disturbing objects generate a nearly
identical contribution to both, the first Q-component and the
second Q-component, while the object contributes predominantly to
the first Q-component. Similar to the embodiment illustrated in
FIG. 8, a way to derive the first Q-component may be to downmix the
receive signal using the signal of the first frequency that is used
to generate the exciting magnetic field as an Local Oscillator (LO)
Signal and to likewise downmix the receive signal using the signal
of the second frequency to receive the second Q-component.
[0068] The method further comprises determining a corrected
quadrature component 164 by subtracting the second Q-component from
the first Q-component, which cancels the contributions of all
disturbing objects to a great extent. The information on the
position of the object is determined based on the corrected
Q-component having only little contributions of disturbing objects,
which may, therefore, provided for a good localization result.
[0069] It should be noted that subtracting is only one particular
way to decrease the contributions caused by disturbing objects
within the receive signal based on the two measurements. Other
embodiments may determine the information on the position of the
object using the first quadrature component and the second
quadrature component by other means while achieving similar or
equal results.
[0070] In some embodiments, the method further comprises scaling
the first quadrature component or the second quadrature component
by a scaling factor. Scaling at least one of the two Q-components
may consider that the receive signal is depending on the derivative
of the Magnetic flux through the loop antenna and, therefore,
contributions to the receive signal are higher for higher
frequencies. Considering this observation by means of an
appropriate scaling factor may increase the extent of the
cancellation of the contribution of the disturbing objects.
[0071] Some embodiments may further correct for long term drifts of
the system. According to those embodiments, a change of the
corrected quadrature component is determining and evaluated
continuously. The change of the corrected quadrature component is
corrected if a characteristic of the corrected quadrature component
fulfills an error correction criterion. The error criterion serves
to distinguish a receive signal caused by an object of interest
from a change caused by other effects, such as for example
temperature induced long term drifts of the system. It is noted
that a previously determined correction is maintained even if the
error correction criterion is no longer fulfilled, that is, if an
object to be located is present.
[0072] According to some embodiments, the corrected quadrature
component is minimized if the error correction criterion is
fulfilled. This may, for example, be achieved by adjusting a drift
term that is subtracted from the complex valued representation of
the receive signal.
[0073] The error criterion may evaluate different conditions to
distinguish a receive signal caused by an object of interest from a
change caused by other effects. According to some embodiments, the
error correction criterion is fulfilled if the corrected quadrature
component is below a threshold. According to some embodiments, the
error correction criterion is fulfilled if a gradient of the change
of the corrected quadrature component is below a threshold or if
both conditions apply at a time.
[0074] According to some embodiments, the long-term effects are
compensated by direct super-position of a correction signal on the
receive signal, that is the compensation is not performed based on
the complex valued representations of the receive signal at the
different frequencies. To this end, the superimposed correction
signal may be phase inverted with respect to the receive signal and
exhibit a similar amplitude (deviating, e.g., less than 5% or 10%
from the amplitude of the receive signal). According to some
embodiments, direct superposition of the correction signal is
achieved by superposing the correction signal to the receive signal
in the analog domain. The superposition is performed before analog
to digital conversion to, e.g., derive the complex valued
representation of the receive signal.
[0075] Although primarily illustrated and explained with respect to
the detection of goals in a soccer match, further examples of the
present invention may be utilized in any other scenario where it is
desirable to determine information on the position of a movable
object or of any kind of object. This may, for example, be any
other kind of sports game, such as for example, handball, American
football, polo, cricket, hockey, ice hockey or the like.
Furthermore, examples may be utilized to track the transportation
of movable goods within a warehouse or the like. For example, it
may be of interest if a particular shelf of a storage rack holds
goods or not or to automatically track when merchandise is
transferred from one shelf to another shelf of the rack. In another
implementation, examples of antenna systems may be utilized to
detect the crossing of joggers or cyclists or other competitors at
the start line of a mass sports event or the like.
[0076] Further, the previously described examples and embodiments
mainly use loop antennas to receive the receive signal. Further
embodiments my also use different types of sensors capable to
determine magnetic fields for the same purpose, such as for example
hall sensors, giant magnetoresistance (GNR) Sensors, tunnel
magnetoresistance (TMR) sensors, superconducting quantum
interference devices (SQUIDS) or the like.
[0077] An example of an antenna system for generating a receive
signal for an embodiment of a method for determining information on
a position of an object can be characterized as an antenna system
(2a-d) for determining the transit of an object (11) through an
area of interest within a detection plane (22), the object (11)
emitting a magnetic field (12), the antenna system (2a-d)
comprising at least one loop antenna (4c) for receiving the
electromagnetic field (12), the at least one loop antenna (4c)
comprising one or more antenna loops arranged only within an
antenna plane, the antenna plane being perpendicular to the
detection plane (22); the at least one loop antenna (4c) further
comprising a signal terminal (60) for providing a receive signal
(44a, 44b), the receive signal (44a, 44b) comprising information on
a position of the object (11).
[0078] In example 2 of the antenna system (2a-d), the at least one
loop antenna (4c) is furthermore operable to emit an exciting
electromagnetic field (10), the exciting electromagnetic field (10)
exciting the object (11) to the emission of the magnetic field
(12).
[0079] In example 3, in the antenna system (2a-d) of example 2, the
at least one loop antenna (4c) comprises a first terminal (26a) and
a second terminal (26b) for receiving an excitation signal (28) to
generate the exciting electromagnetic field (10), wherein the
excitation signal (28) is transferred from the first terminal (26a)
to the second terminal (26b) via a first signal path (30a) and via
a different second signal path (30b) of the at least one loop
antenna (4c).
[0080] In example 4, in the antenna system (2a-d) of example 3, the
first signal path (30a) comprises a first conductor segment
extending in parallel to the detection plane (22) and wherein the
second signal path (30b) comprises a second conductor segment
extending in parallel to the detection plane (22).
[0081] In example 5, in the antenna system (2a-d) of example 4, the
first signal path (30a) and the second signal path (30b) are
arranged on different sides of the detection plane (22) and with
essentially identical distance to said detection plane (22).
[0082] In example 6, in the antenna system (2a-d) of any of
examples 3 to 5, the first signal path (30a) and the second signal
path (30b) are configured such that the excitation signal (28)
propagates from the first terminal (26a) to the second terminal
(26b) via the first signal path (30a) and the second signal path
(30b) simultaneously and in phase.
[0083] In example 7, in the antenna system (2a-d) of any of
examples 3 to 6, the first terminal (26a) is situated between a
first coil (64a) being part of the first signal path (30a) and a
second coil (64b) being part of the second signal path (30b), the
first coil (64a) and the second coil (64b) having windings of
opposite orientation.
[0084] In example 8, in the antenna system (2a-d) of example 7, the
first coil (64a) and the second coil (64b) are part of a
transformer (62), the transformer (62) further comprising a third
coil (66) coupled to the first coil (64a) and the second coil (64b)
such that essentially no current is induced in the third coil (66)
when the current through the first coil (64a) and the second coil
(64b) is essentially equal.
[0085] In example 9, in the antenna system (2a-d) of example 8, the
signal terminal (60) comprises a first signal terminal (60a)
coupled to a first side of the third coil (66) and a second signal
terminal (60b) coupled a different second side of the third coil
(66) in order to provide the receive signal at the first signal
terminal (60a) and the second signal terminal (60b).
[0086] In example 10, the antenna system (2a-d) of any of the
preceding examples further comprises a compensation signal
generator coupled to the loop antenna (4c), wherein the
compensation signal generator is operable to compensate differing
currents in the first signal path (30a) and in the second signal
path (30b) such that the currents in the first signal path (30a)
and in the second signal path (30b) become essentially equal.
[0087] In example 11, in the antenna system (2a-d) of example 10,
the compensation signal generator comprises a compensation signal
path (32) with adjustable coupling characteristics, the
compensation signal path coupled (32) to one signal path of the
first signal path (30a) and the second signal path (30b).
[0088] In example 12, in the antenna system (2a-d) of example
11,the compensation signal path (32) comprises a conductor wire
being essentially parallel to one signal path of the first signal
path (30a) and the second signal path (30b), the conductor wire
comprising at least one of an adjustable distance to the one signal
path and an adjustable inductance (58) and capacitance.
[0089] In example 13, the antenna system (2a-d) of any of the
preceding examples further comprises a calibration signal generator
(69) operable to modify the characteristics of the antenna system
(2a-d) such that a signal is generated at the signal terminal
(60).
[0090] In example 14, in the antenna system (2a-d) of example 13,
the calibration signal generator (69) comprises a calibration
circuit, the calibration circuit being coupleable to the first
signal path (30a) or the second signal path (30b) such that a
characteristic of the respective signal path is altered.
[0091] In example 15, in the antenna system (2a-d) of example 13,
the calibration signal generator (69) is operable to select one of
a first ground loop signal path (70a) and a second ground loop
signal path (70b), each ground loop signal path, when selected,
closing an electrical circuit between the first terminal (26a) and
the second terminal (26b) of the antenna system (2a-d).
[0092] In example 16, the antenna system (2a-d) of any of the
preceding examples further comprises, at a border of the area of
interest, at least one further loop antenna (6c) for receiving the
electromagnetic field, the further loop antenna (6c) comprising one
or more antenna loops arranged only within a further antenna plane,
the further antenna plane being perpendicular to the antenna plane
and parallel to the detection plane (22).
[0093] In example 17, the antenna system (2a-d) of any of the
preceding examples further comprises a signal evaluator (68)
coupled to signal terminal (60) of the antenna system (2a-d), the
signal evaluator (68) being operable to determine a signal
indicative of the object (11) passing through the area of interest
when a phase condition of the receive signal (44a, 44b) received at
the signal terminal (60) changes according to a predetermined
condition.
[0094] In example 18, in the antenna system (2a-d) of example 17,
the predetermined condition is a phase change of the receive signal
(44a, 44b) from positive phase terms to negative phase terms or
vice versa.
[0095] In example 19, the antenna system (2a-d) of any of the
preceding examples further comprises a mounting structure (24)
adapted to mount the antenna system (2a-d) to a support structure
(18) such, that the detection plane (22) has a predetermined
distance to a predetermined position at the support structure
(18).
[0096] In example 20, in the antenna system (2a-d) of example 18,
the support structure is a post or a bar (18) of a soccer goal,
wherein the object is a soccer ball (11) and wherein the
predetermined distance corresponds to half a diameter of a soccer
ball.
[0097] An example of a goal for generating a receive signal for an
embodiment of a method for determining information on a position of
an object can be characterized as having coupled thereto at least
one of the antenna systems of any of the preceding examples at a
predetermined distance to a goal line.
[0098] A first Example of an objects or sport equipment for
emitting a magnetic field in response to an exciting
electromagnetic field (10), can be characterized as comprising
three loop antennas (14a-c) being arranged in pairwise
perpendicular orientation with respect to each other, the three
loop antennas (14a-c) being coupled to a resonator (16), the
resonator (16) having a resonance frequency corresponding
essentially to the frequency of the exciting electromagnetic field
(10).
[0099] In example 2, in the object or sports equipment of the first
example, each loop antenna (14a-c) is connected in series or in
parallel to an associated capacitance (16a-c) such as to form three
independent resonators, each having a resonance frequency
corresponding essentially to the frequency of the exciting
electromagnetic field (10).
[0100] In example 3, in the object or sports equipment of example 1
or 2, the resonance frequency is from the range of 10 kHz to 300
kHz or from the range of 30 kHz to 200 kHz.
[0101] The description and drawings merely illustrate the
principles of the invention. It will thus be appreciated that those
skilled in the art will be able to devise various arrangements
that, although not explicitly described or shown herein, embody the
principles of the invention and are included within its spirit and
scope. Furthermore, all examples recited herein are principally
intended expressly to be only for pedagogical purposes to aid the
reader in understanding the principles of the invention and the
concepts contributed by the inventor(s) to furthering the art, and
are to be construed as being without limitation to such
specifically recited examples and conditions. Moreover, all
statements herein reciting principles, aspects, and examples of the
invention, as well as specific examples thereof, are intended to
encompass equivalents thereof.
[0102] The aspects and features mentioned and described together
with one or more of the previously detailed examples and figures,
may as well be combined with one or more of the other examples in
order to replace a like feature of the other example or in order to
additionally introduce the feature to the other example.
[0103] Examples may further be or relate to a computer program
having a program code for performing one or more of the above
methods, when the computer program is executed on a computer or
processor. Steps, operations or processes of various
above-described methods may be performed by programmed computers or
processors. Examples may also cover program storage devices such as
digital data storage media, which are machine, processor or
computer readable and encode machine-executable,
processor-executable or computer-executable programs of
instructions. The instructions perform or cause performing some or
all of the acts of the above-described methods. The program storage
devices may comprise or be, for instance, digital memories,
magnetic storage media such as magnetic disks and magnetic tapes,
hard drives, or optically readable digital data storage media.
Further examples may also cover computers, processors or control
units programmed to perform the acts of the above-described methods
or (field) programmable logic arrays ((F)PLAs) or (field)
programmable gate arrays ((F)PGAs), programmed to perform the acts
of the above-described methods.
[0104] The description and drawings merely illustrate the
principles of the disclosure. Furthermore, all examples recited
herein are principally intended expressly to be only for
pedagogical purposes to aid the reader in understanding the
principles of the disclosure and the concepts contributed by the
inventor(s) to furthering the art. All statements herein reciting
principles, aspects, and examples of the disclosure, as well as
specific examples thereof, are intended to encompass equivalents
thereof.
[0105] A functional block denoted as "means for . . . " performing
a certain function may refer to a circuit that is configured to
perform a certain function. Hence, a "means for s.th." may be
implemented as a "means configured to or suited for s.th.", such as
a device or a circuit configured to or suited for the respective
task.
[0106] Functions of various elements shown in the figures,
including any functional blocks labeled as "means", "means for
providing a sensor signal", "means for generating a transmit
signal.", etc., may be implemented in the form of dedicated
hardware, such as "a signal provider", "a signal processing unit",
"a processor", "a controller", etc. as well as hardware capable of
executing software in association with appropriate software. When
provided by a processor, the functions may be provided by a single
dedicated processor, by a single shared processor, or by a
plurality of individual processors, some of which or all of which
may be shared. However, the term "processor" or "controller" is by
far not limited to hardware exclusively capable of executing
software, but may include digital signal processor (DSP) hardware,
network processor, application specific integrated circuit (ASIC),
field programmable gate array (FPGA), read only memory (ROM) for
storing software, random access memory (RAM), and non-volatile
storage. Other hardware, conventional and/or custom, may also be
included.
[0107] A block diagram may, for instance, illustrate a high-level
circuit diagram implementing the principles of the disclosure.
Similarly, a flow chart, a flow diagram, a state transition
diagram, a pseudo code, and the like may represent various
processes, operations or steps, which may, for instance, be
substantially represented in computer readable medium and so
executed by a computer or processor, whether or not such computer
or processor is explicitly shown. Methods disclosed in the
specification or in the claims may be implemented by a device
having means for performing each of the respective acts of these
methods.
[0108] It is to be understood that the disclosure of multiple acts,
processes, operations, steps or functions disclosed in the
specification or claims may not be construed as to be within the
specific order, unless explicitly or implicitly stated otherwise,
for instance for technical reasons. Therefore, the disclosure of
multiple acts or functions will not limit these to a particular
order unless such acts or functions are not interchangeable for
technical reasons. Furthermore, in some examples a single act,
function, process, operation or step may include or may be broken
into multiple sub-acts, -functions, -processes, -operations or
-steps, respectively. Such sub acts may be included and part of the
disclosure of this single act unless explicitly excluded.
[0109] Furthermore, the following claims are hereby incorporated
into the detailed description, where each claim may stand on its
own as a separate example. While each claim may stand on its own as
a separate example, it is to be noted that--although a dependent
claim may refer in the claims to a specific combination with one or
more other claims--other examples may also include a combination of
the dependent claim with the subject matter of each other dependent
or independent claim. Such combinations are explicitly proposed
herein unless it is stated that a specific combination is not
intended. Furthermore, it is intended to include also features of a
claim to any other independent claim even if this claim is not
directly made dependent to the independent claim.
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